Various types of apparatus have been devised to aid in exercising muscles by exerting a muscle or muscle group against the opposing force of a weight, a spring, a resilient band or another muscle. One example is U.S. Pat. No. 2,613,932 to Manners for an apparatus that enables the legs to work against the force of springs attached to the shoulders. Another is U.S. Pat. No. 3,162,441 to Karlik which utilizes an arrangement of cables to allow the user to move arms and legs in opposition to each other. In U.S. Pat. No. 4,441,707 to Bosch the arm muscles can work against each other by means of a line that goes around the user's back.
Apparatus have also been devised specifically for exercise of the abdominal muscles. U.S. Pat. No. 4,775,148 to the present inventor employs a spring and belt combination by which the user can exert the abdominal muscles against the resistive force of a spring. U.S. Pat. No. 4,824,105 to Goldenberg has an inflatable bag that presses inward upon the abdomen for the same purpose.
The apparatus described above place the external force, to be resisted, generally over the entire abdominal area. It would be convenient be able to localize the muscle area upon which the external force is brought to bear. The user could then select particular muscle groups to exercise. The user could also work upon increasing the definition of certain abdominal muscles. It follows, therefore, that an apparatus which would allow the user to apply an external force against selected abdominal muscles would have considerable utility.